The Lotrščak Tower (Croatian: Kula Lotrščak) is a fortified tower located in Zagreb, Croatia, in old part of town called Gradec or Gornji grad (English: Upper town). The tower, which dates to the 13th century, was built to guard the southern gate of the Gradec town wall. The name is derived from Latin campana latrunculorum 'thieves' bell', referring to a bell hung in the tower in 1646 to signal the closing of the town gates.
In the 19th century a fourth floor and windows were added to the Lotrščak Tower and a canon was placed on the top, called the Grič cannon. The canon is fired every day at noon.